Design Of High-Accuracy Clock Synchronization For Distributed Measurement System Based On PTPv2

Wind tunnel is a kind of tube equipment which can produce and control air flow manually,and it is one of the most common and effective tools in aerodynamic experiment.The air flow is driven and controlled by the power equipment inside the pipe to simulate the air flow around high-speed objects,and measure the physical effect of the air flow on the tested objects by the measurement system deployed in the wind tunnel.There are many subsystems in the measurement system deployed in wind tunnel,and the measurement devices,objects and requirements of each subsystem are different.All subsystems must be tested jointly to provide measurement data.Therefore,it is required that all measuring devices with different bus types and different acquisition methods operate under the same time base,so that the measured data are consistent and comparable in time.Precision time protocol(PTP)is defined by IEEE 1588 standard.It can realize the high-accuracy time synchronization of distributed system by technologies of network communication and local computing.It fills the vacancy that neither NTP nor GPS can cover well,it is specially designed for the local system that needs time accuracy beyond NTP,and there is no high cost of GPS signal receiver installed in every node of GPS,besides,it avoids the problem of inaccessibility of GPS signal.With the development of packet-switch technology,the revised IEEE 1588-2008 standard defines the version 2 of PTP.In this thesis,the measurement system deployed in a large wind tunnel in China is taken as the research object.The main works are as follows:(1)According to the electrical interface,protocol support and synchronization accuracy requirements,the main measuring devices of the eight subsystems of the target measurement system are sorted and analyzed.Clock synchronization schemes and suitable time stamp schemes are proposed for the devices.The influence of network configuration and load on clock synchronization is tested.According to the results of experiments,a synchronization network architecture is designed.Besides,an experimental network with the same topology is built,which verifies the effect of the design.(2)Aiming at the requirements of high-accuracy synchronous acquisition between the force measurement subsystem and attitude angle measurement subsystem in the target system,the measurement and correction methods of the transmitting delay of the signal channels of the two subsystems are studied.A special device is designed to share and adjust delay of clock and trigger signal.The device corrects the transmitting delay of the signal channel of the target subsystem to reduce the acquisition time error between the target systems by changing the relative delay of the clock and the trigger signal.(3)The mathematical model of the mechanism of PTP clock synchronization is established,and the model is modified by introducing the factors that affect the accuracy of clock synchronization.An adaptive interference compensation PTP clock synchronization algorithm based on stable fast transversal recursive leastsquares algorithm is designed and simulated.The work product includes a complete synchronized time base scheme,special device to share and adjust delay of clock and trigger signal based on FPGA and an adaptive PTP clock synchronization algorithm.